A basic understanding of the physiology of the retina requires a rigorous demonstration of the neurotransmitter systems which function during visual information processing. This proposal is designed as a biochemical approach to the important, yet unresolved problem of identification and characterization of retinal neurotransmitters. The overall goal of this project is to a) identify the functional neurotransmitters in the retina. b) determine the cellular and subcellular localization of specific neurotransmitter systems and c) relate the biochemical and morphological characteristics of neurotransmitter systems to the current concepts of the physiology of vision. Biochemical techniques and assays have been developed by the principal investigator for in vitro qualification and quantitation of uptake, storage, and release of neurotransmitter substances in neuronal preparations. These techniques include rapid perfusion of chemically stimulated retinal synatosomal fractions, with subsequent biochemical analysis of perfusates and electron microscopic and autoradiographic analysis of the stimulated retinal fractions. The success of these biochemical and microscopic techniques in brain preparations, and in results of preliminary retina studies, strongly demonstrate the effectiveness of these approaches in the proposed study. The significance of this work is twofold. First, it will produce significant information about retinal neurotransmitter physiology, clarify some aspects of retinal pharmacology and provide some new understanding into the basic cellular mechanisms which regulate the specific neuronal cell types in the retina. At the same time, this information will be useful in formulating a model for other more complex and less accessible neuronal systems, in terms of how NT systems are localized and what control mechanisms determine their final output. BBLIOGRAPHIC REFERENCES: Cotman, C.W., Nadler, J.V., Redburn, D.A., Vaca, K.W. and White, W.F. Characterization of Putative Amino Acid Transmitter Release from Slices of Rat Dentate Gyrus. J. Neurochem. (1977), in press. Redburn, D.A. Analysis of 14C-GABA Uptake and Release from Rabbit Retina Synaptosomes. in press Exp. Eye Res. (1977).